Electrical time-limit switch.



P. K. STERN.

ELECTRICAL TIME LIMIT SWITCH.

APPLIOATION FILED MAR. 18, 1902.

947,981 Patented Feb. 1, 1910.

2 SHEET88HEET 1.

Winesses;

P. K. STERN.

ELBGTRIGAL TIME LIMIT SWITCH.

APPLICATION FILED MAR. 18, 1902.

947,981. Patented Feb. 1, 1910. 2 SHEBTSSHEET 2.

I P U m E92 m w l T 2 11L E" M 9 4 IFD J4 W :'I .5 mmww" a I I h Mbwe/zhr W/ j If UNITED STATES, PATENT OFFICE.

PHILIP STERN, OF NEW YORK, N. Y., ASSIGNOR TO GENERAL ELEGTBIC COMPANY,A CORPORATIQN OF NEW YORK.

ELECTRICAL TIME-LIMIT SWITCH.

Specification of Letters Patent.

Application filed March 18, 1902.

Patented Feb. 1, 1910.

Serial No. 98,762.

To all whom 'it may concern:

Be it known that I citizen of the United cit of New York, in the countyand State of New York, have invented certain new and useful Improvementsin Electrical Time- Limit Switches, of which the following is aspecification.

My invention in time-limit electrical switches relates to that class ofelectrical switches having an electromagnetic motor, usually in the formof a solenoid disposed between the bridges of the switch for releasing acatch hook, upon the overload of electrical current carried by thecircuit wires and conductors in which the switch is included, wherebysuitable projecting springs ars disposed in connection with the bridgesof the switch, to throw the same into an open position when the catchhas'heen struck by a plunger or armature of the electromagnetic motor orsolenoid aforesaid. In thls connection my improvements have relation toa means whereby an overload may be maintained for a desired period oftime betore the circuit of which the switch forms part, is interrupted.

I am aware that, previous to my invention in automatic time-limitswitches, means have been employed in connection with switches of thischaracter for limiting the time of the overload by means of clockworkand analogous devices.

It is the object of my invention to provide a means carried b the switchbase, which is more sim le an efiective in its operation and less lia 1eto err than those of which I.

am at present aware, or previous to my invention, and particularly lessso than that class employing clockwork to accomplish the same ob ect.

Another object of my invention is to devise a means of the characterstated, for lim- Pn'imr K. STERN, a j tates, l'tSldlilg in the i showing iting the time of the overload for electrical i circuits, which maybe readily applied to switches of the character known as bridgingcontact electrical switches.

In carrying out my invention I have illustrated the disposition of mytime-limiting devices for two difierent types of switches in the twosheets of drawings hereto annexed, which form part of thisspecification, and in whichtil Fi re 1 is a front elevation of anelectrlca switch of the bridging contact patter-u.

two solenoid electromagnets with which accomplish the purpose of myinvention, illustrated in section, the section being taken through thetwo solenoid magnets and cores verticall Fig. 2 illustrates a similar.disposition 0 the time-limit features, showing the manner in which thetwo solenoids co-act when one. is placed vertically over the other. Inthis figure I have shown a side elevation of an electrical bridgingcontact switch of a somewhat narrower and longer pattern than thatillustrated in Fig. 1. In the two figures I have shown the manner bywhich I carry out the details of the same principle employed in the onecase on a wide and rather short switch, and in the other. a somewhatelongated and narrow ty e; and Fig. 3 'is a detailed viewof an in ex foradjusting the time-li1nit, and another index for the strength of thecurrent during the interval of time for which the aforesaid index hasbeen set.

In the drawings, similar characters of reference indicate similar parts.

In applying the time-limit principle aforesaid to switches of thischaracter I have considered the adaptation of a retard ing medium, suchas that of a viscous fluid contained in a closely fitting chamber inwhich the solenoid plunger is adapted to move in a manner whcreb thefluid will be required to be displace by the plunger through calibratedapertures permitting only of a predetermined quantity of transfor of theviscous fluid from the cylinder or chamber in which it is confined, toan escaping cylinder in which it is withheld and caught as the plungeris drawn into the solenoid by the magnetic action of the field of forcegenerated by the current as it circulates around the convolutions of thesolenoid; and to this end I have preferred the use of such viscous fluidas glycerin, well boiled, so as to eliminate air and moisture from thesame, whereby the adhesion of the fluid to the walls of the cvlindcr orchamber in which it is confined during its resisting force against. thesolenoid. may be as nearly uniform and constant as possible; and inemploying prepared glycerin for the purpose of maintaining the. greatestconstancy of the solenoid in the manner aforesaid, l have con tructedthe confining chamber or cylinder. together with the retaining cylinan,in a manner whereby the same will any possibility of moisture bepractically moisture-proof so as to avoid ing'absorbed by the glycermwhile the switch is in long continued use in dam or steamy atmospheressuch as would e encountered when applied to switch-boards or panelboards in dynamo or engine rooms. It is well known that glycerin in itsalmost chemically pure condition isextremely hygroscopic, and whenconsiderable moisture ias been absorbed by the gl cerin the value of itas a" retarding agent ecomes unknown and, unless such precaution isresorted to against the accumulation of moisture, the time-limitfeatures of the switch could not be depended upon.

In carrying my invention into practice I have preferred to describe thesame in con nection with that type of switch in which the projectingmechanism for throwing the switch bridges into an open position, 1s 111.

the form of a spring energized plu er A,

and since I do not propose to claim t is as any part of my invention, anextended description of the same is not deemed necessary, as any meanswhereby the switch may be thrown into an open position will be readilyunderstood by those who are skilled in the art to which my inventionappertains. The manner in which the pro'ectmg device is released b theusual solenoid and plunger 0 C, 'is l' ewise of that'character which isfamiliar to those who have made a study of automatic electrical circuitbreakers, and is therefore sufliciently clear in the illustration torequire no particular description. My invention therefore will beconfined to that part of the circuit-breaking system con- 1 tainedwithin the solenoid B and its combination with the solenoid C and itsconcomitants. Extending within the solenoid B, is a tubular casing Dbetween the head E of the inner tubular.fluid-containing chamber D andtheupper guide M, connected to the solenoid, the upper end of saidchamber D, bein in ement with an inner threaded portion E 0 such guide,for the purpose of rigidly hol sai tube to its bearing in the head eextremity of the cas' relation with the. gui e M, by means of gasketsand confining rings ably clamped by set screws G G. In the upper portionof the fluid-containing chamber D are a series of small outlets f, ti,whereb the glycerin F contained in e fluid c amber is allowed to escape,as will be hereinafter more fullyexplained. At the opposite extremity ofthe fluid chamber D are similar openings f, f arranged in valve-tightconnection with corresponding openings h, h formed in the lower upturnedinner ortion i and iof the outer casing D. e arrangement of theaforesaid openings h, h and f, f is D is in fluid tlg l ili.

such as to form a sort of stop cock at the lower extremity ofthe-confining chamber D and outer casing D whereby upon rotating theouter casin D by the milled head H, communication etween the outer casinD and confining chamber D may be cut 0 or established after the mannerof a valvetight vstop cock. This 'feature of my invention afi'ords onemeans of limiting the time in which the glycerin is allowed to circulatebetween t e upper openings 1 and j, the lower 0 enings aforesaid, andthe intzrior of the con ning chamber at its lower en Within theconfining chamber D' is a core of inductive material 1,. closely fittingthe w'alls of the confining chamber in a manner so that no glycerin willbe permitted to pass between the line of division of the perimeter ofthe cylindrical surface of the core I, and the internal cylindricalsurface of the confinin chamber D. To carry the core I so that its poleI may be introduced to different distances in the solenoid B, I providean adjustable rest in the form of a column or spindle J, which passesthrou h a stuffing box which is rovided wit the usual glan packing.ormed in the column or spindle J is a spline In; and a key K, slidmggyenlgag'ed in the spline issecured to the fix co ar-K of the casing,which latter is secured by rivets, screws or other mechanical means, tothe lower extremity of the fluidcontaining chamber D. Upon shifting thecolumn or spindle J b the milled head or thumb piece L, whic is retainedby screw 1 and engaging shoulders Z and Z", a vertical movement may beimparted to the column-or spindle so as to adjust the ole I of the corein the zone of magnetic in uence of the solenoid B. Thus it will bereadily understood how I am enabled to vary the magnetic inductionbetween the solenoid B and the pole I of the core I, as well as thecirculation of the glycerin F in the confining chamber D, outer casin'D, and communicatin openin f, f, and h.

Sli ingly p aying in the integral guide M is a ta pet m, adapted to iminge against a pivote lever N, as the core Pis drawn into the solenoid Bb -d namic induction sufli- 'ciently'to strike t e ower extremity of thetappet m, so as to raise the same and effect the movement of the leverN. The purpose of the leverN is to raise the sliding tube 0' and'plunger 0' of the solenoid C so as to bring the pole I sufiicientlywithin the the p magnetic induction of the solenoid C to en-' I with itsconcomitants, while illustrated in the usual manner for tripping thespringactuated mechanism of the circuit-breaker, is disposed in a mannerwhereby my time limit solenoid magnet B and its concomitants areconjointly operating to produce rupture of the circuit of which theswitch forms part. when the overload has become of such a character thatwill induce a sutli cient number of lines of magnetic force to raise thecore of the solenoid'B' against the retarding effect of the glycerin F.in that time for which the retarding effect has been predetermined bythe position of an index Q, denoting the number of seconds or minutesallotted for operation.

It will be understood by a careful study of the conditions that the twosolenoidal systems co-act with each other upon a time limit for anoverload, while on instantaneou overloads they operate independently.The function of this will be clear when a study of the solenoid C isresorted to independently of the solenoid B. As an explanatory example,a so-called ,short circuit may be considered as an excess of overloadover that which the circuit is designed to carry, and under whichconditions the switch would simply act as a circuit-breaker operatingunder the control of the solenoid C. The plunger 0' being previously setto its lowest extrei'nity. or to a position which would be comnu-nsuratewith the operation of the same by a current circulating around thesolenoid t". for a given short circuit expressed in the value of currentstrength in amperes, will project the plunger 0' violently into themagnetic field of the solenoid to a sufficient extent to bring the polepiece 1" into contact with the releasing catch as aforesaid, in a.manner to release the switch and break the circuit: but in the meantime,due to the retarding effect of the glycerin upon the plunger 1. thesolenoidal system B will not have had a sufficient time within which toeffect a rupture of the circuit by the performance of its function uponthe lever N, and in this sense the switch would operate merely as a.circuit-breaker. On the other hand however. should the over load beinsufficient to raise the plunger 0' into the magnetic field of force ofthe solenoid .-the plunger I being adjusted to operate. on a current:strength having a smaller valuewill be drawn into the magnetic field ofthe solenoid P). but being retarded by the resisting force due to thecontined glycerin F, the circuit-breaking plunger (Y will not besufficiently introduced into its magnetic field aforesaid until the polel of the plunger 1 shall have contacted with the tappet m, in a mannerso asto raise the lever N and tube 0 which carries the plunger O asaforesaid. and in this sense the two solenoidal systems B and G areinterdeendent. It, will thus be understood by my invention that I amenabled to provide a means whereby a circuit-breaker having a constantlyacting retarding means may be adjusted so as to maintain an overload onthe circuit which it designed to protect for a predetermined period, andat the same time instantly rupture the same circuit upon an excessiveoverload.

A feature of my invention which 1 consider important in connection withcircuitbreakers, which is a characteristic of the particular manner inwhich I carry out the principles aforesaid. lies in the re-adjustment ofthe releasing mechanism to its normal condition after the overload hassubsided. In explanation of this feature the movement of the plunger I.must be under the influence of a current of C value. for a time T. andif T has not been sufficient to effect the release of thespringprojccting mechanism before the value of C has fallen the breakerwill not be tripped. This feature of my invention involves a principleof considerable value on motor circuits where an excessive overloadfrequently occurs during the starting up period for short intervals oftime, the apparatus which the circuit-breaker is designed to protectbeing constructed with a sufficient overload factor to operate onoverloads of but short duration.

In Fig. 3, the solenoid I) and its core F provided for the time limitoverload. are located in lower vertical alinement with respect to thesolenoid C and its core designed for rupturing the circuit on an instantaneous overload, the core I resting upon a pedestal J, the verticalposition of which can be regulated by hand adjusting means L. while thevertically movable tappet m playing in the top of the casing T). hasconnections with a shifting pin J for the upper core said connectionsincluding hand operable means If for adjusting the vertical position ofthe latter pedestal relatively to the core The inner confining chamberl) for the glycerin. has the upper and lower series of openings f*, f.the latter cooperating with the openings 12 of the upturned innerportion l) of the outer casing, in a manner corres unuling with that ofthe similar parts in the construction disclosed in Fig. i.

In Fig. 3. Q designates the index for in di-ating the retarding periodof the time limit overload. while the index Q correspondingly serves forthe adju tment providing for the strength of the current, during theinterval of time for which the retarding index has been set.

The operation will be readily comprehended. Upon an excessive overload.the solenoid C will elevate its core to trip the latch P, release themotor and operate the switch, such movements being accom lished entirelyindependent of the solenoid 2 and concomitant parts. When the limit ofthe lower abnormal overload riod is reached, the core I will contactwith the tappet m, raise the same and effect the lifting of the core 0into the area of magnetic influence of the solenoid C so that said corewill theninstantaneousl rise, trip the latch and opcrate the switcHaving described my invention so that those skilled in the art to whichit appertains could construct, apply and make use of the same, I claimas new and desire to secure by Letters Patent of the United States 1.The combination with an electric circuit, of a freel movable member foropening said circult, actuating means for said member responsive topredetermined current in said circuit and normally so related to saidmember that said actuatin means is unable to move said member, and meansresponsive to other redetermined current conditions whereby t e relativeposition of said actuating means and said member is varied to enablesaid actuating means to move the said member.

2. The combination with an electric circuit having an electroma neticcoil, of a freely movable member 0 magnetic material so related to thecoil that normally said member lies beyond the efl'l ctive magneticfield of said coil when the current has a predetermined value, and meansfor movin said member into the effective magnetic field of said coil inresponse to a flow of current having said predetermined value.

3. The combination with an electric circuit having an electromagneticcoil therein, of a freely movable member composed of magnetic materialand normally beyond the effective field of said coil when the currenttherein has a predetermined value, and means including a time limitdevice for movin said member into the effective field of said coil undercertain other current conditions whereby said coil is enabled to actuatesaid member.

4. The combination with an electric circuit having an electro-magneticcoil therein, of a freely movable armature normally beyond the effectivemagnetic field of said coil when the current therein has a predeterminedvalue, and means responsive to current of another predetermined valuefor movin said armature into the efl'ective field of sai coil to enablesaid coil to move said member, said second means including a ma neticcoil and a movable member actuate thereb a fluid containing cylinder forretarding t e movement of said latter member, re ulating means forvarying the flow of flui and means for adjusting the position of saidlatter member with respect to its coil.

5. The combination with an electric circuit, of a freely movable member,actuating means for moving said member in response to a redeterminedcurrent flowing in said circuit, a support for said movable member, asecond member operatively related to said support, and means for movingsaid second member and said support in response to certain other currentconditions to a position enabling said actuating means to move saidmember under said current conditions.

6. The combination with an electric circuit, of a freely movable member,actuating means for moving said member in response to a predeterminedcurrent flowing in said circuit, a support for said member, a secondmember provided with a time'limit device and operatively related to saidsupport, and means for moving said second member and said support inresponse to certain other current conditions to a position enabling saidactuating means to move said member under said current conditions. i

7. The combination, twb electromagnetic coils, a free core for one coil,a support for said core, and a core for the other coil having a timelimit device and operatively connected to said su port to change therelati.ve position of the rst core and its 0011 under certain currentconditions in said coils.

8. The combination with an electric circuit, of a movable member, anelectromagnetic coil in said circuit and so related to said movablemember that said movable member is actuated thereby in response to apredetermined current flowing in said circuit, and means for changin therelative positions of said coil and mem er under certain other currentconditions, to enable said coil to move said member to actuate saidmovable member in response to current values less than saidpredetermined amount.

9. The combination with an electric circuit, ofa circuit breakercomprising a switch and restraining means therefor, electromagneticalloperated devices including a member and means to actuate it to trip saidrestrainin means upon a redetermined overloa of current in sai circuit,and a second member operatively associated with said first member forbringing it lnto operative relation to its actuating means under certainother conditions of overload.

10. The combination with an electric circuit, of a circuit breakercomprising a switch and restraining means therefor, an electromagneticcoil and a movable member of magnetic material so related that normallvunder certain conditions of overload in said circuit'the movable memberlies beyond the effective magnetic field of said coil while undercertain other conditions of overload said member lies within said field,

and means for-moving said member into the effective magnetic field ofsaidcoil during the first of said conditions of overload.

11. The combination with an electric circuit, of a circuit breakercomprising a switch and restraining means therefor, an electromagneticdevice including a movable element arranged to trip said restrainingmeans, and means for moving said movable element into the effectivemagnetic field of said electromagnet under certain conditions ofoverload in said circuit.

12. The combination with an electric circuit, of a circuit breakercomprising a switch and restraining means therefor, an electromagneticcoil, a movable member for causing the release of said restrainingmeans, said movable member bein normally out of the effective magneticfie d of said electromagnet, and means for moving said member into saidmagnetic field upon a predetermined overload in said circuit.

13. The combination with an electromagnet and a movable member actuatedthereby, of a time limit device therefor comprisin a pair of cylindersarranged the one wit in the other and having a communicating assageway,means for adjustin the size 0 the passageway, and an adjusta le supportfor said movable member within said cylinders.

14. In combination with an electromagnet and a movable member actuatedthereby, of a'time limit device therefor comprisin a pair of cylindersarranged the one wit in the other, a communicating opening throu h theinner cylinder, and means actuated y the rotation of the other cylinderto vary the size of said opening.

In testimony whereof, I have signed my name to this specification in thepresence of two subscribing witnesses.

PHILrP K. STERN.

Witnesses STEPHEN TEUcIcK, M. BLUMEB.

